Controls for the park brake or park lock on tractors having power-shuttle transmissions are typically one of two known types. The first type has a park position on a shift lever that also controls forward, neutral, and reverse operation of the transmission. The second type uses a separate mechanical park brake lever, which allows use of a three position shuttle lever. A possible shortcoming of the first type is a greater space requirement for accommodating shifting between four positions, which can result in occasional inadvertent shifting into park. A possible shortcoming of the second type is that because the shuttle lever and brake lever are separate, the shuttle lever can be operated while the park brake is inadvertently engaged.
Thus, what is sought is a transmission shift control operable for selecting forward, reverse, neutral and park modes, without requiring a separate park position so as to provide relative compactness, yet which reduces or eliminates the possibility of inadvertent shifting into park, and operating the transmission in the forward and reverse modes while the park brake or lock is inadvertently actuated or applied.